Development of a Data Acquisition System for the MiCES Small Animal PET Scanner

We have previously reported on the design of a firewire (1394a) based data acquisition system for small animal positron emission tomography (PET) scanners. Here we report on the evolution of that design for our micro-crystal element mouse PET scanner - MiCES. The scanner utilizes 72 position sensitive photomultiplier tubes (PMT), each coupled to a 22×22 array of 0.8×0.8×10 mm MLS crystals. Each electronics module supports two PMTs. The module consists of digital and analog boards. The digital board contains a field programmable gate array (FPGA), a microcontroller, and a firewire transport device. We are building two versions of the analog board. One version uses a 32 channel amplifier and pulse height analyzer application specific integrated circuit (ASIC) from Integrated Detectors and Electronics. This version processes each signal from the PMT (12 per tube) independently. The second version uses an analog ASIC from Concorde Microsystems Inc. This version uses resistive summing to combine the PMT signals into the 4 analog channels processed by the ASIC. In both cases, the analog board is a daughter board on the digital board, and the two configurations are supported by different microcode loaded into the FPGA. The resulting 36 sets of detector boards are connected to a host Macintosh computer via the firewire bus. Another microcontroller in the gantry acts as a master controller and is connected to the Macintosh host via a serial cable. The master controller provides command signals (e.g., stop, start, reset, etc) to the detector boards as well as supporting all gantry motions, and sends data to the host via firewire at regular intervals to report the current table and gantry positions.